Video processing system for demultiplexing received compressed and non-compressed video signals and transmitting demultiplexed signals

ABSTRACT

The present invention is intended to permit both real-time display of a picture represented by a non-compressed video signal on a television and display of a picture represented by a compressed video signal at any desired time by simultaneously transmitting the compressed video signal and non-compressed video signal via one interface. An STB packetizes a compressed video signal, and multiplexes the compressed video signal and a blanking signal combined with a non-compressed video signal. Thus, both the video signals are transmitted simultaneously. A picture represented by the non-compressed video signal is displayed on a television in real time. The compressed video signal is stored in a storage medium incorporated in the television, read at any user&#39;s desired time, and decoded so that a picture represented by the compressed video signal can be viewed at the user&#39;s desired time.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2005-185925 filed on Jun. 27, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a transmission method for a digitalvideo signal, and a video processing system, for example, a set-top box(STB) that receives a digital television signal or a television displaydevice.

2. Description of the Related Art

Along with both the prevalence of high-definition(HD) televisions(TV)reaping the benefit of digital terrestrial broadcasting and the sale ofBlu-ray recorders capable of recording high-definition TV programs, theneed for digital video interfaces via which a high-qualityhigh-definition video signal is transmitted to televisions withoutdeterioration of picture quality has been increased these days. Thestandards for interfaces supporting transmission of a non-compressedvideo signal include the digital visual interface (DVI) standards whichare formulated by the Digital Display Working Group (DDWG), and thehigh-definition multimedia interface (HDMI) standards to be licensed bya limited liability company (LLC). Moreover, the standards forinterfaces supporting transmission of a video signal compressed based onthe MPEG standards or the like include the IEEE 1394 standard and thestandards for local-area networks (LANs). A related art in which theinterface supporting transmission of a non-compressed video signal isadapted to a television is described in, for example, Non-patentDocument 1. This literature discloses a technology for multiplexing anon-compressed video signal that is not transformed into packets (thatis, not packetized), and information on the format for the video signalwhich is packetized. Moreover, the HDMI standards stipulate that audiodata is also packetized and transmitted. A related art for adapting theinterface, which supports transmission of a compressed video signal, toa television is described, for example, in Non-patent Document 2.Moreover, copyright protection technologies devised based on the abovestandards include, for example, the high-bandwidth digital contentprotection (HDCP) system that treats the non-compressed video signal andthe digital transmission content protection (DTCP) system that treatsthe compressed video signal.

Moreover, the serial digital data interface (SDDI) system forpacketizing both a non-compressed video signal and a compressed videosignal and transmitting them in sequence over a single line isdescribed, for example, in Patent Document 1.

Patent Document 1: Japanese Unexamined Patent Publication No. 8-307455

Non-patent Document 1: Written Standards CEA-861-B, U.S. CEA, 2002

Non-patent Document 2: Written Standards CEA-775-B, U.S. CEA, 2004

SUMMARY OF THE INVENTION

The number of types of signal sources will presumably increase, andtelevisions will be requested to include input interfaces via which anon-compressed video signal and a compressed video signal respectivelyare received. However, two types of interfaces that require differentconnectors are included in a television (a television receiver or thelike), a connector space must be preserved and two types of cables mustbe prepared. Patent Document 1 discloses the system for transmitting thenon-compressed video signal and compressed video signal simultaneously.The transmission system is suitable for broadcasting stations. In otherwords, it is hard to implement the transmission system described inPatent Document 1 in a television for general home use because thenon-compressed video signal is packetized.

Moreover, the number of copyright protection technologies to be employedincreases along with an increase in the number of types of interfaces tobe handled. Nevertheless, the increasing number of copyright protectiontechnologies should be properly implemented.

The present invention addresses the foregoing problems. An object of thepresent invention is to provide a technology relevant to an interfacevia which both a non-compressed video signal and a compressed videosignal can be transmitted. Another object of the present invention is toprovide a technology capable of appropriately protecting a copyright.

In order to accomplish the above objects, the present invention ischaracterized in that a received compressed video signal is decoded inorder to produce a non-compressed video signal, that the compressedvideo signal is combined with a blanking signal contained in thenon-compressed video signal, and that the resultant video signal istransmitted. Moreover, the present invention is characterized in that acompressed video signal that is packetized is combined with anon-compressed video signal that includes synchronizing (hereinaftersync) signals and is not packetized, and that the resultant video signalis transmitted. Owing to the constituent features, both thenon-compressed video signal whose transmission method is determinedbased on, for example, the DVI or HDMI standards, and the compressedvideo signal whose transmission method is determined based on, forexample, the IEEE 1394 standard or the like can be transmitted via onetype of interface. This obviates the necessities of preserving the spacefor two connectors and preparing two types of cables, and leads to adecrease in a cost.

Moreover, the second constituent feature of the present invention is toperform a plurality of pieces of encipherment on video signals to betransmitted or received via one interface, and to select one of theplurality of pieces of encipherment. The selection may be achieved inresponse to an enciphered change instruction issued from a user.

According to the present invention, an interface to be used in commonbetween the non-compressed video signal and compressed video signal canbe provided. Moreover, a copyright can be preferably protected.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, objects, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram showing a first embodiment of a videoprocessing system in accordance with the present invention;

FIG. 2 is a block diagram showing an example of the configurations of atransmission unit and a reception unit included in the video processingsystem;

FIG. 3 shows an example of the structure of a packet of a compressedvideo signal;

FIG. 4 is a block diagram showing a second embodiment of the videoprocessing system in accordance with the present invention;

FIG. 5 is a block diagram showing a third embodiment of the videoprocessing system in accordance with the present invention;

FIG. 6 is a block diagram showing the flow of a video signal in thevideo processing system of the third embodiment;

FIG. 7 shows an example of the circuitries of an output circuit and aninput circuit respectively included in the third embodiment;

FIG. 8 shows an example of the basic circuitries of an output circuitand an input circuit respectively included in a video processing system;

FIG. 9 is a block diagram showing a fourth embodiment of the videoprocessing system in accordance with the present invention; and

FIG. 10 shows an example of the circuitries of an output circuit and aninput circuit respectively included in the fourth embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, the preferred embodiments of the presentinvention will be described below. The present invention simultaneouslytransmits both a non-compressed video signal and a compressed videosignal via a common (the same) interface. The transmission is achievedwhile the connectivity via a non-compressed digital interface such as aDVI interface or an HDMI interface that is prevailing is held intact. Inthe embodiments to be described below, a video processing systemincludes a set-top box (STB) with, for example, a built-in digital tunerand a television display device (hereinafter a television). Needless tosay, the embodiments can be adapted to the other video processingsystems.

First Embodiment

FIG. 1 is a block diagram showing the first embodiment of the presentinvention. The first embodiment includes a set-top box (STB) 11 that isan example of a video processing system, a television 12 that is anotherexample of the video processing system, and a mobile viewer 13 making itpossible to view a picture in any place other than a home. Examples ofactions to be performed by these pieces of equipment will be describedbelow.

The STB 11 receives a radiofrequency signal 101 sent through digitalbroadcasting or over a cable. A digital tuner 111 demodulates atransport stream (hereinafter a TS) carried by a compressed videosignal. A TS/PS converter 112 samples a program stream (hereinafter aPS) from the demodulated TS. A decoder 113 produces a non-compressedvideo signal. A video synthesizer 114 synthesizes the non-compressedvideo signal with an on-screen-display (OSD) screen picture produced byan OSD unit 115. The non-compressed video signal is not transformed intopackets (that is, not packetized) but is transmitted from a transmissionunit 117 to a reception unit 127 included in the television 11 via avideo signal interface 103. The non-compressed video signal received bythe reception unit 127 is transferred to a display unit 129 via a videosynthesizer 124. The display unit 129 displays a real-time screenpicture according to the non-compressed video signal, and thus presentsthe picture to a user. Control units 116 and 126 control multiplexing tobe performed by the transmission unit 117 and reception unit 127 andalso control communicating circumstances. Moreover, the control unit 126informs the STB 11 of the displaying ability of the television 12, andthe control unit 116 matches the format for a video signal to betransmitted from the STB 11 with the display-related characteristics ofthe television 12. Furthermore, the control units 116 and 126 transferremote-control control codes so as to control bidirectionalcommunication so that the STB 11 and television 12 can be interlockedwith each other.

On the other hand, a TS output of the digital tuner 111 and an OSDoutput of the OSD unit 115 are transferred to the transmission unit 117.The transmission unit 117 combines the TS and OSD packets with anon-compressed video signal so as to produce a multiplex video signal,and transmits the multiplex video signal to the reception unit 127 viathe interface 103. The reception unit 127 separates the multiplex videosignal into the non-compressed video signal and the TS and OSD packets.The TS and OSD packets separated or sampled by the reception unit 127are stored in a storage medium 128. The storage medium 128 is realizedwith, for example, a hard disk. Alternatively, a semiconductor memorysuch as a flash memory will do. Thus, a picture is recorded based on theTS. The stored TS is read from the storage medium 128 in response to auser's instruction. A TS/PS converter 122 samples a PS, and a decoder123 produces a non-compressed video signal. At the same time, OSD datais read from the storage medium 128, if necessary. An OSD unit 125 usesthe OSD data to produce a non-compressed OSD video signal. A videosynthesizer 124 synthesizes the OSD video signal with the non-compressedvideo signal sent from the decoder 123. A picture represented by thenon-compressed video signal produced by synthesizing the stored videosignal with the OSD data is displayed on the display unit 129. A usercan view the motion picture at any desired time.

As long as the television 12 includes the digital tuner 121, thetelevision 12 can receive a digital television signal in the same manneras the STB 11 can. The TS carried by the television signal is stored inthe storage medium 128, and the picture represented by the TS can beviewed at any desired time. Furthermore, the video synthesizer 124 maysynthesize a non-compressed video signal received through the TS/PSconverter 122 and decoder 123 with a non-compressed video signal sentfrom the STB 11 so that two screen pictures can be simultaneouslydisplayed on the display unit 129. Alternatively, the digital tuners 111and 121 may receive signals that fall within different channels, and thesignals may be synthesized in order to display two screen pictures.Otherwise, a video signal falling within one channel supported by aterrestrial digital tuner and a video signal falling within anotherchannel supported by a cable TV tuner may be synthesized in order todisplay two screen pictures. Supposing the STB 11 includes the digitaltuner 111 that is different from the digital tuner incorporated in thetelevision 12 (that is, the digital tuner supporting a channel which isnot supported by the digital tuner incorporated in the television 12), apicture represented by the signal falling within the channel which isnot supported by the television 12 can be viewed in real time or at anydesired time. Moreover, after the STB 11 is dismounted from thetelevision 12, a picture represented by a video signal received by theSTB and stored in the storage medium 128 can be viewed.

As long as the digital tuner 111 concurrently supports a plurality ofchannels, a compressed video signal and a non-compressed video signal tobe combined by the transmission unit 117 may represent differentprograms. Moreover, a compressed video signal to be combined by thetransmission unit 117 may not carry a TS but may carry a PS into whichthe TS is converted. Compared with the TS, the PS has the merit that anamount of data to be transmitted is smaller.

A compressed video signal stored in the storage medium 128 is furthercompressed or subjected to code conversion by a code converter 130 inorder to change transmission methods. Thereafter, the video signal istransferred to a storage medium 138 by way of the interface 131, aninterface 104, and an interface 132 that are compatible with theuniversal serial bus (USB) or conformable to the IEEE 1394 standard.After the video signal is transferred, the mobile viewer 14 isdisconnected by unplugging the interface 104 and becomes portable to anyplace. In the mobile viewer 14, a decoder 133 decodes the video signalstored in the storage medium 138, and a picture is displayed on adisplay unit 139 according to the video signal. Thus, a user can use themobile viewer 14 to view a desired picture in any place.

FIG. 2 is a block diagram showing an example of the configurations ofthe transmission unit 117 and reception unit 127 respectively. Theactions of the transmission unit 117 and reception unit 127 will bedescribed below. Audio data 202 relevant to a non-compressed videosignal sent from the video synthesizer 114 (FIG. 1), a TS output 203 ofthe digital tuner 111 (FIG. 1), and OSD data 204 sent from the OSD unit115 (FIG. 1) are transferred to packet production blocks 211, 212, and213 respectively included in the transmission unit 117. The packetproduction blocks 211 to 213 produce packets, which can be properlycombined with a non-compressed video signal, according to the receivedsignals. The packets produced by the packet production blocks 211 to213A are transferred to a buffer 214. In the buffer 214, the packets aresorted by packet transmission priority, and then transmitted orderlyduring a period corresponding to the pulse duration of a blanking signalcombined with the non-compressed video signal. An error-correcting codeencoder 215 inserts an error-correcting code to the packets sorted inthe buffer 214. A rearrangement block 216 rearranges the packets bit bybit so as to improve durability against a burst error, and thentransmits the resultant packets to a multiplex encoder 217. Themultiplex encoder 217 includes a multiplexer 401 that combines therearranged packets with a non-compressed video signal sent from thevideo synthesizer 114 (FIG. 1), a copy flag appending block 402 thatappends a copy control flag for the non-compressed video signal, anencipherer 403 that enciphers a video signal, and a transmission encoder404 that encodes a signal to be transmitted. The output of the multiplexencoder 217 is transmitted as a multiplex video signal to an inputcircuit 228 included in the reception unit 127 via an output circuit218.

The multiplex video signal received by the input circuit 228 istransferred to a multiplex decoder 227. The multiplex decoder 227includes a transmission decoder 411 that decodes an encoded signal, adecipherer 412 that deciphers a video signal, a copy flag sampling block413 that samples a copy flag, and a demultiplexer 414 that separates thenon-compressed video signal 201 and packets from one another. Adisarrangement circuit 226 disarranges the packets so as to reproduceoriginal signals. An error-correcting code decoder 225 corrects anerror, and transmits the resultant signals to a buffer 224. The signalscarrying the packets are temporarily held in the buffer 224, and thentransmitted to packet decoders 221 to 223 respectively. The packetdecoders 221 to 223 decode the packets received from the buffer 224, andproduce audio data 292 relevant to the non-compressed video signal, a TS293, and OSD data 294 respectively. These data items are shown in FIG. 1to be transmitted from the reception unit 127 to the storage medium 128.

A capability informer 229 gives the information on the displayingcapability of the television (specifications for display and/ordisplay-related characteristics) to a capability discriminator 219 overa communication channel 208. The capability discriminator 219discriminates the displaying capability of the television 12 accordingto the information on the displaying capability, and transmits a resultof discrimination 205. The result of discrimination 205 is transmittedto the control unit 116 (FIG. 1). The control unit 116 controls thecomponents of the STB 11, which are engaged in handling or transmittinga video signal, so that a video signal will be transmitted in a formatsuitable for the connected television 12. Moreover, the control unit 116checks the displaying capability of the television 12 and transmits amultiplex video signal employed in the present embodiment. Owing to theforegoing configurations, the multiplex video signal is not transmittedto a television that is not designed to receive the multiplex videosignal (that is, a television including a conventional interface) but anon-compressed video signal along is transmitted thereto. Namely, theconnectivity to a television including a conventional interface isensured. As the component that informs the capability of the television12, for example, an extended display identification (EDID) systemstipulated by the Video Electronics Standards Association (VESA) shouldpreferably be adopted. In the present embodiment, the information on thedisplaying capability of the television includes, for example, thehorizontal and vertical resolutions of the display unit 129, a colorrendering index, and a gamma. For effective utilization of the presentembodiment, the information on the displaying capability of thetelevision may further include, for example, a timing of displaying apicture represented by a multiplex video signal, a bit rate of acompressed video signal, a list of decodable coding techniques, thestorage capacity of the storage medium 128, an available capacity, and amaximum recording speed.

The capability informer 229 and capability discriminator 219 are alsoused to authenticate equipment or check an enciphering ability.According to, for example, the DVI or HDMI standards, the high-bandwidthdigital content protection (HDCP) system licensed by a limited liabilitycompany (LLC) is adopted as the encipherment technique. Along with thediversity of contents, it may be necessary to manage a plurality ofencipherment techniques in association with the contents or nations inthe future. In the present embodiment, a video signal receiving side mayinclude facilities that implement a plurality of equipmentauthentication techniques or a plurality of encipherment techniques, andan automatic identification/selection circuit may be included foridentifying and selecting an appropriate technique by referencing aprotocol based on which a transmitting side initiates equipmentauthentication. On the other hand, the transmitting side may include anautomatic identification/selection circuit that identifies a kind ofcontent and a nation where a television is used, and selects anappropriate encipherment technique. For example, a region code recordedon a digital versatile (or video) disk (DVD) is read and used to selectan encipherment technique. For a television signal, a broadcastingstation may be identified and an encipherment technique may be selected.

A specific encipherment technique may have to be constantly adopted dueto national regulations or regulations imposed by an entrepreneur. Inthis case, if a dedicated video processing system is newly prepared, acost of development increases. Therefore, a video processing system isprovided with a plurality of encipherers that can implement a pluralityof kinds of encipherment, and an identification/selection circuit thatidentifies a kind of encipherment and selects an encipherer according tothe result of the identification. At this time, theidentification/selection circuit may autonomously identify and select akind of encipherment. Moreover, a designation circuit may be includedfor allowing a user to designate a kind of encipherment. Moreover, thedesignation circuit may be used to designate one of the pieces ofencipherment at a factory prior to delivery. In this case, a procedurefor changing the designation of encipherment (for example, entry of acommand or a password at the STB 11 or television 12) may be hiddenbehind a user for fear the user may use the designation circuit tochange the kind of encipherment into another. Assuming that thedesignation of encipherment has to be changed after delivery, aprocedure for changing the designation of encipherment may be able to bereceived in the form of a television signal or downloaded from theInternet under a specific condition (for example, a user has to pay afee). Thus, the hidden procedure of changing the designation ofencipherment is disclosed to a user under the specific condition, andthe user can change encipherment from one kind to another. This servicemay be provided when the present embodiment is implemented. Otherwise,the procedure for changing the designation of encipherment may be storedin a storage medium such as a DVD, and the DVD may be supplied as adesignation change DVD to the user.

Furthermore, when various kinds of encipherment are used, picturequality may be modified by restricting a resolution or a bit rate of acompressed video signal according to the grade of encipherment.

Communication circuits 220 and 230 perform bidirectional communicationover a communication channel 209 and thus allows the control units 116and 126 shown in FIG. 1 to transfer control information to or from eachother. For example, bidirectional communication based on the consumerelectronics control (CEC) protocol stipulated in the HDMI standards maybe adopted as the bidirectional communication employed in the presentembodiment. Moreover, if an error uncorrectable by the error-correctingcode decoder 225 occurs, the television 12 transmits a request forretransmission to the STB over the communication channel 209. The STB 11may respond to the retransmission request and retransmit a compressedvideo signal that is affected by the error. This permits error-freerecording. An identification number or symbol such as a time stamp maybe appended to a packet of a compressed video signal contained in amultiplex signal 207 produced by combining the compressed video signalwith a non-compressed video signal. The television 12 may transmit theidentification number or symbol assigned to an error-stricken packettogether with the retransmission request to the STB 11. Consequently,when the retransmission request is issued, the STB 11 may check theidentification number or symbol of the error-stricken packet so as toretransmit the original packet of the error-stricken packet alone. Sincethe STB 11 need not retransmit error-free packets, transfer efficiencyimproves.

Transmission of packets from the buffer 214, that is, sorting of packetsby priority will be described below. The capacity for transmission ofpackets to be combined with a non-compressed video signal is limited. Apacket to be transmitted as a top priority is audio data that isrelevant to the non-compressed video signal and that is needed to bereproduced in real time synchronously with a video signal. Therefore,the priority of an audio packet relevant to the non-compressed videosignal is set to the highest priority, and the disposition of the audiopacket in a data stream is determined as a top priority. A packet of acompressed video signal and a packet of OSD data are disposed in theremaining part of the data stream. The priorities of the compressedvideo packet and OSD packet are determined arbitrarily. When the OSDpacket relates to a non-compressed video signal (or highly relatesthereto), the priority of the OSD packet may be higher than that of thecompressed video packet. When the possibility that the television 12 mayutilize the compressed video signal is high, the priority of thecompressed video packet may be higher than that of the OSD packet.

For transmission of a compressed video signal to the storage medium 128,packets should be arranged for fear a maximum recording rate supportedby the storage medium 128 may be exceeded. Otherwise, the flow ofpackets over the communication channel 209 may be controlled in order tocontrol the number of packets to be transmitted. When the television 12reproduces a compressed video signal in nearly real time, the number ofpackets to be transmitted has to be controlled based on an encoding ratefor the compressed video signal.

Depending on a format for a non-compressed video signal, the packettransmission ability may be insufficient for combining a compressedvideo signal. In this case, a clock whose pulses are synchronous withpixels represented by the non-compressed video signal is multiplied by n(where n denotes a value equal to or larger than 2). Otherwise, a formatspecifying that the pulse duration of a blanking signal combined withthe non-compressed video signal is extended may be adopted. Thus, theability to transmit a packet of a compressed video signal improves.

FIG. 3 shows an example of the structure of a packet of a compressedvideo signal. As shown in FIG. 3, a packet of a TS includes a header offour bytes long, and adaptation (or payload) of one hundred andeighty-four bytes long, and comes to one hundred and eighty-eight bytesin total. In order to transmit the TS during an interval betweentransmissions of a non-compressed video signal (for example, a blankinginterval), the packet size should be smaller. In FIG. 3, a packet to betransmitted is composed of a header of three bytes long and payload oftwenty-eight bytes long. The TS packet of one hundred and eighty-eightbytes long is segmented into pieces of payload to be contained in sevenpackets of compressed video signals.

An example of the structure of a header will be described below. Thefirst byte represents a packet type such as a packet of a compressedvideo signal or audio data. The second and third bytes of sixteen bitslong in total represent the order of one of seven sections of a TSpacket (three bits), a TS packet number (eleven bits), and a copycontrol flag (two bits). The TS itself includes a time stamp. The timestamp may be used to exclude the eleven bits of the TS packet numberfrom the header. For convenience' sake, the TS packet number should beincluded in the header. The TS packet number is used as anidentification number with which a packet is identified. If atransmission error occurs, the identification number is checked in orderto designate a packet whose retransmission is requested.

For example, assuming that a high-definition video signal is transmittedat a frequency of 20 Mbps, one million and sixty thousand TS packets ofone hundred and eighty-eight bytes long are transmitted during onesecond. If a transmission error occurs, a retransmission request isissued to a transmitting side. In this case, since the baud rate of thecommunication channel 209 is low (that is, a transfer rate is low), if100 ms is needed for transmission of error information, TS packetnumbers with which at least ten thousand TS packets are identified areneeded. Fourteen bits are needed in order to represent a TS packetnumber. The header of eleven bits long is therefore insufficient for theTS packet number. On the other hand, the payload included in the seventhpacket of a compressed video signal has eight bytes left unused. Onebyte out of the available bytes may be used to state part of the TSpacket number that overflows the header. Needless to say, two or threebytes may be used. Moreover, the copy flag may be stated using theavailable bytes but not be stated in the header. If some bytes are stillleft unused and available, the frequency of copy, a storage time duringa picture capable of being viewed at any desired time can be stored,and/or a copy generation management system-digital (CGMS-G) signal canbe stated. If more information need be stated, eight packets ofcompressed video signals other than seven packets may be allocated toone TS packet.

Second Embodiment

FIG. 4 is a block diagram showing another embodiment of the presentinvention. In the present embodiment, the transmission unit 117 andreception unit 127 included in the system configuration shown in FIG. 1are replaced with a transmission unit 230 and a reception unit 250respectively shown in FIG. 4. In the present embodiment, thetransmission unit 230 and reception unit 250 are interconnected via aninterface including three data lines 271, 272, and 273 over which avideo signal is transmitted and a clock line 274 over which a clock istransmitted. The three data lines are used to transmit respectivenon-compressed video signals of, for example, red, green, and blue. Theclock line is used to transmit a reference clock synchronously withwhich data or a video signal is received. Moreover, ten data items shallbe transmitted over the data lines during the cycle of the clock thatpasses through the clock line. Multiplex encoders 231 to 233 and 235,output circuits 241 to 244, input circuits 251 to 254, and multiplexdecoders 261 to 264 are equivalent to the multiplex encoder 217, outputcircuit 218, input circuit 228, and multiplex decoder 227 respectively.The description of the components will be omitted. The description ofthe other blocks shown in FIG. 2 will be omitted.

The case where a switch 245 selects a clock feeder 234 is equivalent tothe embodiment shown in FIG. 2. In the present embodiment, whenhigh-speed transmission of video data is needed, the connections throughthe switch 245 are switched to select the multiplex encoder 235. In thiscase, the clock line is used as a data line in order to make an amountof transmitted video data four-thirds times larger. In this case, thereference clock synchronously with which input data is reproduced by thetelevision 12 is not a clock to be transmitted over the clock line, butthe reference clock is sampled from a signal sent over each data line.Therefore, all or at least one of signals received by the input circuits251 to 254 respectively should be routed to a phase-locked loop (PLL)256 in order to sample a clock component from the input signal. Forsampling of the clock component, a bandpass filter or the like should beused in combination with the PLL. Needless to say, a digital locked loop(DLL) may be substituted for the PLL.

Various formats are adaptable to video data, and numerous referenceclocks are usable. In the case where a clock is sampled from a data lineand adopted as a reference clock, the cycle of the reference clock needbe detected accurately. The detection is quite time-consuming. In thepresent embodiment, in an initial state, the switch 245 selects theclock feeder 235 and routes a reference clock sent from the clock feeder235 to the reception unit 250 over the clock line 274. Consequently, thereception unit 250 is readily informed of the cycle of the referenceclock. Consequently, the present embodiment is advantageous in terms ofthe reduction in the time required for initialization to be performed inrelation to the cycle of the reference clock.

Using the component that provides the STB 11 with the information on thedisplaying capability of the television 12 and that is described inconjunction with FIG. 2, the transmission unit 230 is informed of thefact whether the reception unit 250 supports a mode in which the clockline is used as a data line. Moreover, the time required for detectionof the cycle of a clock to be performed as part of initialization can beinformed in the same manner. Using the bidirectional communicationchannel 209 shown in FIG. 2, the reception unit 250 can inform thetransmission unit 230 of the fact that the initialization is completed.

Third Embodiment

FIG. 5 is a block diagram showing another embodiment of the presentinvention. The present embodiment has the same system configuration asthe one shown in FIG. 1 except that the transmission unit 117 andreception unit 127 are replaced with a transmission unit 240 and areception unit 260 which have the same configurations as those shown inFIG. 4. The same reference numerals are assigned to components identicalto those shown in FIG. 4. The present embodiment includes the PLL shownin FIG. 4 as a component. However, the PLL is not shown in FIG. 5 forbrevity's sake. The present embodiment further includes an input circuit255, a multiplex decoder 265, a multiplex encoder 258, and an outputcircuit 257 which are not included in the embodiment shown in FIG. 4.

In FIG. 5, when data is transmitted using a clock line, the data is nottransmitted from the STB 11 to the television 12 but is transmitted fromthe television 12 to the STB 11. In an initial state, the output circuit257 is in an off state. Similarly to the embodiment shown in FIG. 4, thetransmission unit 240 included in the STB 11 transmits data and a clockto the reception unit 260. After sampling a clock from each data isinitiated, data can be transmitted over the clock line. After the outputcircuit 244 is driven to the off state, the output circuit 257 isstarted so that the reception unit 260 will transmit data to thetransmission unit 240. At this time, if the cycle of the clock is set tothe same cycle as that attained in the initial state, a clock can besampled from the clock line, over which data is inversely transmitted,in the same manner as it is from any other data line. While data isinversely transmitted over the clock line, video data is kepttransmitted over the data lines from the transmission unit 240 to thereception unit 260.

FIG. 6 shows an example of the flow of a video signal to be attained ina case where an inverse data transmission facility is included in thesystem configuration shown in FIG. 1. The television 12 transmits acompressed video signal, which is stored in the storage medium 128, tothe STB 11 over the clock line through the inverse data transmission.The TS/PS converter 112 and decoder 113 include din the STB 11 decodesthe compressed video signal into a non-compressed video signal. Thenon-compressed video signal is transmitted back to the television 12over the data line, and a picture is displayed on the display unit 129according to the decoded video signal. Moreover, if OSD data stored inthe storage medium has to be displayed, the OSD data is transmitted tothe OSD circuit included in the STB 11 over the clock line. The videosynthesizer 114 synthesizes the OSD data with the compressed videosignal and transmits the resultant signal to the television 12.

Owing to the inverse data transmission facility, even a televisiondevoid of a decoder can reproduce a video signal stored in the storagemedium and display a picture according to the video signal. The sameapplies to a case where although a television includes a decoder, thedecoder does not support a coding technique used to encode a compressedvideo signal. Furthermore, assuming that transmission of an intenselycompressed television signal to be encoded according to a novel codingtechnique which has not been devised when a television was put on themarket is initiated in order to provide a broadcasting service, therecording facility of the television and the facility thereof permittinga user to view a picture at any desired time can be employed. Moreover,even when a compressed video signal produced using a coding techniqueand a copyright protection technique that are not supported by atelevision are stored in the television, as long as an STB supports thetechniques, the stored compressed video signal may be transmitted to theSTB so that copyright protection and decoding will be performed by theSTB. The video signal having undergone the copyright protection anddecoding is returned as a non-compressed video signal to the television.Eventually, a picture can be displayed based on the video signal.

FIG. 7 shows an example of the circuitries of the input circuits 254 and255 and the output circuits 244 and 257 which are shown in FIG. 5.Before a description will be made in conjunction with FIG. 7, theactions of an input circuit and an output circuit which have the basiccircuitries shown in FIG. 8 will be described below. An output circuit31 includes an output controller 311, transistors 312 and 313, and aconstant current source 314, while an input circuit 32 includes terminalresistors 336 and 337 and a differential discriminator 338.

The output controller 311 switches the states of the transistors 312 and313 so that the states will be a combination of an on state and an offstate or a combination of the off state and on state. When thetransistors 312 and 313 are in the on and off states respectively, thesame current as the one flowing from the constant current source 314flows along a signal line 321, and a voltage is developed across theterminal resistor 336. Since no current flows along a signal line 322,the voltage across the terminal resistor 337 is 0 V. When thetransistors 312 and 313 are in the off and on states respectively, sinceno current flows along the signal line 321, the voltage across theterminal resistor 336 is 0 V. The same current as the one flowing fromthe constant current source 314 flows along the signal line 322, and avoltage is developed across the terminal resistor 337. So-calleddifferential transmission is achieved. The differential discriminator338 detects a potential difference between the terminal resistors, thusa logical level is determined.

The circuitries shown in FIG. 7 are realized by connecting inputcircuits and output circuits, which have the same circuitries as thoseshown in FIG. 8, in parallel with each other. Two output circuitsconnected in parallel with each other are not started simultaneously.The output controller 331 (or 311) included in the output circuit thatis not in operation controls the states of the transistors 312 and 313(or transistors 332 and 333) so that both the states will be the offstates. Both the input circuits may be started, or the terminalresistors 316 and 317 (or 336 and 337) included in the input circuitthat is unused may be disconnected. Moreover, the differentialdiscriminator 318 (or 338) may be halted in order to reduce the powerconsumption.

Fourth Embodiment

FIG. 9 is a block diagram showing another embodiment of the presentinvention, wherein two televisions 15 and 16 are adopted as videoprocessing systems. Namely, the present embodiment is an embodiment inwhich the STB 11 shown in FIG. 1 includes a display unit and functionsas a television. Similarly to the embodiment shown in FIG. 1, amultiplex video signal having a non-compressed video signal and acompressed video signal combined with each other is transmitted from thetelevision 15 to the television 16 via a video interface 104. A picturerepresented by the non-compressed video signal is displayed on a displayunit 129 included in the television 16. On the other hand, thecompressed video signal is stored in the storage medium 128, andreproduced at any user's desired time so that a picture will bedisplayed on the display unit 129.

FIG. 10 shows an example of the configurations of transmission/receptionunits 157 and 167. In this example, both a data line 271 and a clockline 274 permit bidirectional transmission. The circuitries of an inputcircuit and an output circuit are identical to those shown in FIG. 7.When data is transmitted from the transmission/reception unit 157 to thetransmission/reception unit 167, the data is transferred from amultiplex encoder 231 through an output circuit 241 to each of an inputcircuit 251 and a multiplex decoder 261. On the other hand, a clock istransferred from a clock feeder 235 through an output circuit 244 toeach of an input circuit 254 and a PLL 283. In contrast, when the datais transmitted from the transmission/reception unit 167 to thetransmission/reception unit 157, the data is transferred from amultiplex encoder 282 through an output circuit 281 to each of an inputcircuit 271 and a multiplex decoder 272. On the other hand, a clock istransmitted from a clock feeder 284 through an output circuit 257 toeach of an input circuit 255 and a PLL 274.

As mentioned above, when the television 15 or 16 is provided with thefacility of inversely transmitting a video signal, the actions to bedescribed below will be performed. Specifically, as indicated withdashed lines in FIG. 9, a compressed video signal stored in the storagemedium 128 included in the television 16 is transmitted to thetelevision 15. A TS/PS converter 152 and a decoder 153 included in thetelevision 15 produce a non-compressed video signal, and a picture isdisplayed on a display unit 159 according to the video signal.Alternatively, after a TS/PS converter 122 and a decoder 123 included inthe television 16 produce a non-compressed video signal and transmit itto the television 15, a picture may be displayed on the display unit 159according to the video signal.

According to the present embodiment, two interconnected televisions(video processing systems) can share a digital tuner, a storage medium,a decoder, and various resources required for copyright protection.

In the aforesaid embodiments, an STB and a television are adopted asvideo processing systems. Even when a video signal source such as arecorder or a DVD player and a monitor are paired, the same advantagesas those described above can be expected.

Using the aforesaid embodiments of the present invention, a real-timenon-compressed video signal that is not packetized and a compressedvideo signal that is packetized can be transmitted simultaneously viaone interface. Specifically, a plurality of digital video signalsconformable to different standards can be transmitted via one interface.In a video processing system such as a television to which the presentinvention is adapted, while a picture represented by a non-compressedvideo signal sent from a signal source such as an STB is being displayedon the display unit of the television, a compressed video signal that istransmitted simultaneously can be stored in a storage medium such as ahard disk drive (HDD) incorporated in the television, and a picturerepresented by the compressed video signal can be viewed at any desiredtime. In other words, a real-time picture that is a video content and apicture stored at a different time can be displayed simultaneously onthe same screen. Namely, while the video content is viewed in real time,the stored picture can be viewed at a desired time.

Furthermore, when a physical layer that deals with high-speedtransmission via an interface which supports transmission of anon-compressed video signal is used for data transmission, iftransmission of the non-compressed video signal is unnecessary, manycompressed video signals can be transmitted or a video signal can betransferred quickly.

Furthermore, according to the aforesaid embodiments, various copyrightprotection technologies can be properly coped with. Satisfactory viewingcan be achieved under conditions for fair use.

The present invention is applied to a video signal transmission methodfor multiplexing a non-compressed video signal and a compressed videosignal via one interface. In particular, the present invention willprove effective especially for transfer of a video signal between, forexample, a video signal source such as an STB and a video display devicesuch as a television.

While we have shown and described several embodiments in accordance without invention, it should be understood that disclosed embodiments aresusceptible of changes of modifications without departing from the scopeof the invention. Therefore, we do not intend to be bound by the detailsshown and described herein but intend to cover all such changes andmodifications a fall within the ambit of appended claims.

The invention claimed is:
 1. A video transmission device comprising: amultiplexing processor that multiplexes a compressed video signal and anuncompressed video signal to generate a multiplexed video signal; and atransmitter that transmits the multiplexed video signal generated by themultiplexing processing to an external device; wherein the compressedvideo signal is superimposed on a blanking period of the non-compressionvideo signal; wherein the video transmission device further comprises anencryption processor; and wherein the multiplexing processor multiplexesthe compressed video signal encrypted with a first encryption scheme bythe encryption processing and the non-compression video signal encryptedwith a second encryption scheme by the encryption processing.